Examples of conventional methods for producing liquefied fuel oils using biomass as feedstocks are as follows. In Patent Documents 1 to 3, a liquefaction catalyst for biomass, which is potassium carbonate dissolving in water, and biomass, which is wood chips, are processed at 200 to 385° C., thereby producing a liquefied fuel oil in a yield of 23 to 45 wt % based on the biomass solids content.
In Patent Document 4, wood chips, water, a neutral oxygenated solvent (acetone, methyl ethyl ketone, ethyl acetate, 1-butanol, etc.), and potassium carbonate are processed at 300° C., thereby producing a liquefied fuel oil in a yield of 33 to 68 wt % based on the biomass solids content.
In Patent Document 5, wood chips, water, a phenolic compound (phenol or cresol), and an alkali metal compound or alkaline earth metal compound (potassium carbonate, sodium carbonate, calcium carbonate, sodium hydroxide, calcium hydroxide, etc.) are processed at 350° C., thereby producing a liquefied fuel oil in a yield of 47 to 65 wt % based on the biomass solids content.
In Patent Document 6, cellulosic biomass and one type of organic solvent selected from aliphatic ketones and fatty alcohols (acetone, methyl ethyl ketone, methanol, ethanol, etc.) are subjected to pyrolysis at a temperature equal to or higher than a supercritical temperature in the presence of an activated carbon catalyst, thereby producing a liquefied fuel oil in a yield of about 50 wt % based on the biomass solids content.
In Patent Document 7, lignocellulosic biomass is processed with a supercritical alcohol (methanol, etc.) at 320 to 360° C., thereby producing a liquefied fuel oil that is alcohol-soluble in a yield of about 70 wt % based on the biomass solids content.
In Patent Document 8, biomass is processed with 1-octanol at 195 to 500° C., thereby producing a liquefied fuel oil in a maximum yield of about 90 wt % based on the biomass solids content.
In Patent Document 9, biomass is processed with a mixed solvent obtained by adding 5 to 20 vol % of water to a fatty alcohol having 1 to 8 carbon atoms (methanol, etc.), under supercritical or subcritical conditions for the alcohol, thereby producing a liquefied fuel oil in a maximum yield of 95 wt % based on the biomass solids content.
In Patent Document 10, ligneous biomass is processed with an organic solvent such as anthracene at 250 to 400° C., thereby producing a liquefied fuel oil that is soluble in acetone in a yield of 45 wt % based on the biomass solids content. Part of the liquefied fuel oil produced is circulated for use as a solvent for processing biomass.
In Patent Document 11, ligneous biomass is processed with a mixed solution of polyethylene glycol/glycerol/sulfuric acid=70/30/3 (170 to 200° C.), thereby producing a liquefied fuel oil in a yield of 45 wt % based on the biomass solids content.
Patent Document 1: JP Patent Publication (Kokoku) No. 3-36870 B (1991)
Patent Document 2: JP Patent Publication (Kokoku) No. 3-36871 B (1991)
Patent Document 3: JP Patent Publication (Kokoku) No. 4-75274 B (1992)
Patent Document 4: JP Patent Publication (Kokoku) No. 3-36872 B (1991)
Patent Document 5: JP Patent Publication (Kokoku) No. 3-41516 B (1991)
Patent Document 6: JP Patent Publication (Kokoku) No. 6-29438 B (1994)
Patent Document 7: JP Patent No. 3755076
Patent Document 8: JP Patent Publication (Kokai) No. 2005-288406 A
Patent Document 9: JP Patent Publication (Kokai) No. 2005-296906 A
Patent Document 10: JP Patent Publication (Kokai) No. 2006-063310 A
Patent Document 11: JP Patent Publication (Kokai) No. 2004-075928 A